Liquid adhesives, such as liquid optically clear adhesives (LOCAs), are used in a wide variety of electronic assemblies. For example, liquid adhesive can be used to bond a touch panel to a main liquid crystal display. Liquid adhesive can also be used to bond a protective cover, such as a cover glass or lens, to a touch panel. The use of liquid adhesives to bond substrates in display assemblies, in particular, has a number of advantages. For example, liquid adhesive can improve the durability of a display assembly. In addition, use of liquid adhesive make the display assembly more easy to rework compared to assemblies bonded using adhesive tape.
Since liquid adhesives are in liquid form, they can require special care when applying them to substrates. In particular, care should be taken to ensure that the introduction of bubbles or voids between the substrates is avoided. In addition, care should be taken to avoid inconsistent curing of the liquid adhesive in different locations of the substrates so as to prevent distortions, visible defects in the final product. In addition, pressure applied to the substrates during a curing process should be consistent in order to provide a consistent gap between the substrates. If multiple substrates are bond together in a stack, any inconsistencies in the gaps between the substrates can be exacerbated. This could lead to different stacks having different overall thicknesses, also referred to as Z-height. These factors and others can make it difficult to control process parameters related to liquid adhesive applications in a manufacturing setting. Inconsistent process parameters can lead to high part rejection rates or defects in the visual quality of the final product.